validate_monadic

-module(validate_monadic).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([error/1, succeed/1, map/2, map_error/2, and_also/2, compose/3, and_then/2, and_map/2]).

-spec error(FJZ) -> {ok, any()} | {error, {FJZ, list(FJZ)}}.
error(Err) ->
    {error, {Err, []}}.

-spec succeed(FKE) -> {ok, FKE} | {error, {FKF, list(FKF)}}.
succeed(A) ->
    {ok, A}.

-spec map({ok, FKI} | {error, {FKJ, list(FKJ)}}, fun((FKI) -> FKM)) -> {ok, FKM} |
    {error, {FKJ, list(FKJ)}}.
map(Validation, Map_fn) ->
    gleam@result:map(Validation, Map_fn).

-spec map_error({ok, FKP} | {error, {FKQ, list(FKQ)}}, fun((FKQ) -> FKT)) -> {ok,
        FKP} |
    {error, {FKT, list(FKT)}}.
map_error(Validation, Map_fn) ->
    case Validation of
        {ok, V} ->
            {ok, V};

        {error, {Head, Rest}} ->
            {error, {Map_fn(Head), gleam@list:map(Rest, Map_fn)}}
    end.

-spec and_also(
    {ok, FLG} | {error, {FLH, list(FLH)}},
    {ok, FLG} | {error, {FLH, list(FLH)}}
) -> {ok, FLG} | {error, {FLH, list(FLH)}}.
and_also(Validation_a, Validation_b) ->
    case {Validation_a, Validation_b} of
        {{ok, _}, {ok, A}} ->
            {ok, A};

        {{error, {Err_a_head, Err_a_rest}}, {error, {Err_b_head, Err_b_rest}}} ->
            {error,
                {Err_a_head,
                    gleam@list:concat(
                        [Err_a_rest, gleam@list:prepend(Err_b_rest, Err_b_head)]
                    )}};

        {{error, Err}, _} ->
            {error, Err};

        {_, {error, Err@1}} ->
            {error, Err@1}
    end.

-spec compose(
    FKW,
    fun((FKW) -> {ok, FKX} | {error, {FKY, list(FKY)}}),
    list(fun((FKW) -> {ok, FKX} | {error, {FKY, list(FKY)}}))
) -> {ok, FKX} | {error, {FKY, list(FKY)}}.
compose(Input, Validation, Validations) ->
    gleam@list:fold(
        Validations,
        Validation(Input),
        fun(Acc, Cur) -> and_also(Acc, Cur(Input)) end
    ).

-spec and_then(
    {ok, FLO} | {error, {FLP, list(FLP)}},
    fun((FLO) -> {ok, FLS} | {error, {FLP, list(FLP)}})
) -> {ok, FLS} | {error, {FLP, list(FLP)}}.
and_then(Validation, Bind_fn) ->
    gleam@result:then(Validation, Bind_fn).

-spec and_map(
    {ok, fun((FLX) -> FLY)} | {error, {FLZ, list(FLZ)}},
    {ok, FLX} | {error, {FLZ, list(FLZ)}}
) -> {ok, FLY} | {error, {FLZ, list(FLZ)}}.
and_map(Prev_validation, Validation) ->
    case Prev_validation of
        {ok, Apply} ->
            case Validation of
                {ok, A} ->
                    {ok, Apply(A)};

                {error, Err} ->
                    {error, Err}
            end;

        {error, {Prev_err_head, Prev_err_rest}} ->
            case Validation of
                {ok, _} ->
                    {error, {Prev_err_head, Prev_err_rest}};

                {error, {Next_err_head, Next_err_rest}} ->
                    {error,
                        {Prev_err_head,
                            gleam@list:flatten(
                                [Prev_err_rest,
                                    gleam@list:prepend(
                                        Next_err_rest,
                                        Next_err_head
                                    )]
                            )}}
            end
    end.